Name: how prokaryotic dna is copied
Uploaded: 2026-08-26T08:20:08.548Z
Duration: 2 min 57 s
Channel: JoVE

K12 Standards

Tennessee Academic Standards

High School

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

BIO1.LS1.3

Replication in Prokaryotes

In prokaryotes, DNA replication begins when initiator proteins bind to the origin of replication, a small region of DNA containing a specific sequence of bases, creating a complex.

This complex helps to initially separate the DNA. Then the enzyme DNA helicase binds to it and continues to unwind the DNA by breaking the hydrogen bonds between the complementary strands. The newly opened areas are stabilized by single-stranded DNA binding proteins. Each one can now serve as a template for the synthesis of a new strand of DNA.

The unwinding and synthesis proceeds in both directions from the origin, creating two replication forks. In front of the forks, topoisomerase enzymes bind to the DNA and reduce torsional strain as the molecule unwinds.

Once the strands are separated, another enzyme, primase, synthesizes an RNA primer, a short stretch of RNA complementary to the DNA sequence. The primer provides a place for the enzyme DNA polymerase to add nucleotides complementary to the DNA sequence, creating a new DNA strand in a process called elongation.

DNA polymerase synthesizes DNA in the five prime to three prime direction of the molecule, so the synthesis of this strand, the leading strand, proceeds continuously. The other strand, the lagging strand, has the opposite orientation. Consequently DNA is synthesized in short pieces called Okazaki fragments, elongated from additional RNA primers backwards from the overall direction of movement of the replication fork.

The RNA primers are then excised by enzymes such as RNAs, replaced with DNA, and the DNA fragments are joined together by the enzyme DNA ligase, creating a continuous strand.

DNA replication proceeds around the entire molecule, resulting in two circular DNA molecules. This is considered a semiconservative process, because each molecule contains one old strand and one new strand.

原核生物的复制

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Overview

DNA replication has three main steps: initiation, elongation, and termination. Replication in prokaryotes begins when initiator proteins bind to ...

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Education

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JoVE Core

生物学

Genetics

遗传学

DNA Structure and Function

DNA 的结构与功能

KEY TERMS AND CONCEPTS

关键术语与概念

how prokaryotic dna is copied

Prokaryotic DNA is copied through a coordinated process with three main stages: initiation, elongation, and termination. It begins when initiator proteins bind to the single origin of replication, or ori, on the cell’s circular chromosome. The DNA then copies around the circle in both directions, starting from two replication forks, and this produces two DNA molecules.

Several proteins work together to open and protect the DNA during replication. Topoisomerase cuts one side of the double-stranded DNA phosphate-sugar backbone so the helix can unwind more quickly. Helicase breaks the bonds between base pairs at the fork and separates the DNA into two template strands. Single-strand DNA-binding proteins then stabilize the exposed strands as the fork moves along the chromosome.

DNA synthesis can only happen in the 5’ to 3’ direction. Because of this, the leading strand is made continuously, while the lagging strand is made in short sections called Okazaki fragments. These fragments are about 1000 to 2000 base pairs long.

Research on this process has often used Escherichia coli, a common model organism. E. coli has five DNA polymerases: Pol I, II, III, IV, and V. Pol III does most of the replication and can add about 1,000 base pairs per second. That speed helps the two replication forks copy the 4.6 million base pair chromosome in about 40 minutes. Pol I is also well studied, and its main role is to remove the RNA primers at the start of Okazaki fragments on the lagging strand.

Under favorable growth conditions, E. coli can divide every 20 minutes, which is faster than the time needed to copy the genome once. Scientists found that the cell can start another round of replication before the first one is finished. As a result, daughter cells receive a chromosome that is already being copied and can divide again very quickly.

How Prokaryotic DNA Is Copied

the dna helix

How DNA Stores Genetic Information

DNA stores genetic information that is passed from one generation to the next in organisms and most viruses. It is built from two strands of nucleotides that twist together into a double helix. The story of how scientists uncovered this structure developed step by step over nearly a century. Each DNA strand is made of nucleotides. A nucleotide contains the sugar deoxyribose, a phosphate group, and one of four nitrogen bases: adenine (A), guanine (G), cytosine (C), or thymine (T). Adenine and...

dna packaging

Chromatin and Histones in DNA Packing

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organization of genes

Genes, Introns, and Regulatory DNA

Eukaryotic genes are arranged within DNA along with non-coding regions that help control gene activity. A DNA strand includes genes and intergenic regions, which are the stretches between genes. These regions do not code for proteins, but they can contain important regulatory elements such as promoters, enhancers, and silencers. A gene itself is not a single continuous coding block. It usually contains protein-coding exons and non-coding introns. After DNA is transcribed into pre-mRNA in the...

karyotyping

Chromosome Stains for Detecting Disorders

Chromosome staining helps scientists find genetic disorders by showing the number and physical features of chromosomes. These features appear after DNA condenses into chromosomes during mitosis. Cytogeneticists then stop mitosis and stain the chromosomes to study their banding pattern. The pattern reveals details such as chromosome number, shape, and type. A chromosome description like this is called a karyotype. To create one, scientists take an image of the stained chromosomes and identify...

replication in prokaryotes

Prokaryotic DNA is copied through a coordinated process with three main stages: initiation, elongation, and termination. It begins when initiator proteins bind to the single origin of replication, or ori, on the cell’s circular chromosome. The DNA then copies around the circle in both directions, starting from two replication forks, and this produces two DNA molecules. Several proteins work together to open and protect the DNA during replication. Topoisomerase cuts one side of the...

replication in eukaryotes

Eukaryotic DNA Copying and Telomeres

Eukaryotic DNA copying is tightly regulated and must duplicate many linear chromosomes before cell division. The process is highly conserved and uses many proteins with specialized roles. It moves through initiation, elongation, and termination, and it ends with two complete sets of chromosomes in the nucleus. Eukaryotic replication shares basic steps with prokaryotic DNA replication, but the larger genome and linear chromosomes require more proteins. Replication begins at multiple origins of...

proofreading

DNA Polymerase Fixes Replication Errors

DNA polymerase helps copy DNA and fix mistakes during replication. It adds nucleotides in a sequence that matches the template DNA strand. The enzyme also has a higher affinity for the correct base, which helps keep DNA replication accurate. As new genomic DNA is made, it is synthesized in the 5’ to 3’ direction. In many cells, DNA polymerases have different jobs in this process. DNA polymerase delta and DNA polymerase epsilon can proofread when nuclear DNA is being copied. These polymerases...

mismatch repair

DNA Mismatch Repair in Replication

DNA mismatch repair fixes copying errors that happen during DNA replication. When DNA polymerase makes a mistake, the cell can detect a wrong base pair, such as A with G or T with C, and replace it with the correct nucleotide. This repair system works in both prokaryotes and eukaryotes and depends on several proteins. The Mutator protein family plays a central role in this process. In bacteria such as Escherichia coli, MutS first binds the mismatch. MutL then helps identify which strand is the...

nucleotide excision repair

DNA Damage Repair by Excision

DNA damage repair by excision protects cells from mutagens that can change DNA. Exposure to environmental mutagens can create bulky lesions that bend the double helix or block transcription. If these changes are not repaired, they can lead to mutations and may contribute to cancer or disease, depending on which DNA sequences are affected. Nucleotide excision repair, or NER, is the process that detects and removes this kind of damage. Specialized proteins scan the DNA for a damaged region, then...

mutations

DNA Changes From Point Mutations to UV Damage

Mutations are changes in the DNA sequence. They can happen by chance during DNA copying, or they can be caused by environmental factors such as radiation and chemicals. Scientists also describe mutations by how much DNA they affect, how they change a protein, and whether they happen in body cells or germline cells. Some mutations affect only one nucleotide, which is a point mutation. When a point mutation falls inside a gene, the outcome depends on how the amino acid sequence changes. A silent...

transcription

Transcription and Gene Control

Transcription and gene control explain how cells make RNA from DNA and decide which genes are active. RNA polymerase copies a DNA sequence into RNA, and this is the first step in making a protein from a gene. Many other proteins and control sequences help make messenger RNA, or mRNA, correctly. In eukaryotes, the DNA is first copied into a primary RNA, also called pre-mRNA. This RNA can then be processed into mature mRNA, which serves as the template for protein synthesis. In prokaryotes such...

translation

Protein Synthesis and mRNA Decoding

Protein synthesis begins when ribosomes decode messenger RNA (mRNA) and build a chain of amino acids. This final step of gene expression is called translation. The finished chain is a polypeptide, which can later become a functional protein. Proteins are often called the building blocks of life because they make up much of the body, from muscle fibers to hairs and immune system parts. The instructions for each protein are encoded in genes found in the DNA of every cell. In biology, the central...

bacterial transformation

Griffith’s Mouse Experiment and DNA

Bacterial transformation explains how DNA can move into bacteria and change their traits. Frederick Griffith first noticed this in 1928 while studying pneumonia-causing Streptococcus pneumoniae in mice. He compared one pathogenic strain with one non-pathogenic strain and found that only the pathogenic strain killed the host mice. Griffith made an unexpected discovery when he killed the pathogenic bacteria and mixed their remains with live, non-pathogenic bacteria. The mixture killed the mice,...

key terms and concepts

Explore how prokaryotic DNA is copied, from origin binding and replication forks to leading and lagging strands, polymerases, and fast E. coli division.

How Prokaryotic DNA Is Copied | JoVE K12

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JoVE Core系列通过300多节动画视频课简明易懂地讲解生物学中的关键概念，以及150余段视频展示科学家在现代实验室开展实际研究实验，让生物学变得平易近人。

Virginia  Standards of Learning

HIgh School

Life Science

LS.10

LS.10.a

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

HS-LS1-1

Texas Essential Knowledge and Skills

BIO.6

BIO.6.A

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South Carolina College and Career Ready Science Standards

B-LS1-1.

Characteristics of Life

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the-tree-of-life-bacteria-archaea-and-eukaryotes

The Tree of Life - Bacteria, Archaea, and Eukaryotes

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Compare and contrast existing models, identify patterns, and use structural and functional evidence to analyze the characteristics of life. Engage in argument about the designation of viruses as non-living based on these characteristics.
EXPLANATION: Students begin to develop patterns of living and non-living organisms in kindergarten and build on detailed characteristics of different classifications of living organisms throughout elementary and middle school. Biology 1 discussions introduce viral particles and viral cycles, building on student understanding of living organisms to engage in an argument regarding the classification of a viral particle as either living or non-living.

BIO1.LS1.1

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Evaluate comparative models of various cell types with a focus on organic molecules that make up cellular structures.
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BIO1.LS1.2

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DNA Packaging

Overview

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Organization of Genes

Overview

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Karyotyping

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Replication in Eukaryotes

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Mutations

Overview

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Transcription

Overview
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Translation

Lesson: Translation
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RNA Structure

Overview
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MicroRNAs

siRNA - Small Interfering RNAs

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piRNA - Piwi-interacting RNAs

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conservation-of-protein-domains-over-different-proteins

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Allosteric Proteins-ATCase

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Phosphorylation

Ligand Binding Sites

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Covalently Linked Protein Regulators

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The Equilibrium Binding Constant and Binding Strength

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Protein Complexes with Interchangeable Parts

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Integrate evidence to develop a structural model of a DNA molecule. Using the model, develop and communicate an explanation for how DNA serves as a template for self-replication and encodes biological information.
EXPLANATION: Discussions of DNA in earlier grades have been limited to discussions of genes and the role of genes in the appearance and activities of an organism. Biology 1 represents a student's introduction to a molecular model of a DNA as well as the organization of DNA into genes and genes subsequently into chromosomes. Students should address interactions between genes in proteins which regulate both the shape and reproduction of DNA molecules. It is important to note that not all segments of DNA are transcribed for proteins. Portions of DNA are involved in regulating the expression of genes or affect the structure of the chromosomes (replication origin, centromeres, and telomeres).

How Prokaryotic DNA Is Copied

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